1. The Field of the Invention
The present invention relates generally to manners of manufacturing photonic devices. More generally, the present invention relates to methods for facet coating laser diodes or other photonic devices.
2. The Relevant Technology
Edge-emitting lasers commonly have cleaved edges coated with an anti-reflective (AR) or highly-reflective (HR) coating to control the facet reflectivity. Typically, a number of laser bars are coated at the same time in a thin film vacuum deposition system. In a manufacturing environment it is desirable to coat the facets of a large number of laser bars simultaneously. This is often accomplished by forming a “stack” of laser bars, with each laser bar separated from its neighbor by a spacer bar, as is shown in FIGS. 1A and 1B. However, unless the laser bars and intermediate spacer bars are properly stacked, the laser mirror coating is non-uniform.
With reference to FIG. 1A, depicted is a side view representation of exemplary stacks of laser bars 10, with spacer bars 14 interposed between adjacent laser bars 10. Each spacer bar 14 can have the desired height, length, and width to aid with coating of laser bars 10 with AR or HR coatings. During the manufacturing process, the AR or HR coating is incident upon laser bars 10 and spacer bars 14 at an angle, as represented by the arrows in FIGS. 1A and 1B. In the event that a facet 12 of laser bar 10 is lower in height than a surface 16 of spacer bar 14, spacer bar 14 may shadow laser bar 10. This shadowing prevents uniform coating of surface 12 of laser bar 10, which results in degraded operation of laser bar 10.
Similarly, if surface 12 of laser bar 10 is higher than surface 16 of spacer bar 14, the deposition process on the facet of laser bar 10 will tend to be uniform but an “overspray” will occur on the sidewalls of laser bar 10, as indicated in dotted lines in FIG. 1B. When such “overspray” is excessive, the electrical characteristics of laser bar 10 can be degraded.